In many parts of the world, for example in many North African, Arab or Asian countries, washing machines of a simpler type of construction than in Central Europe are common. Many such machines do not have a drum rotating in a liquor tank, which is configured as a front or top loader, but rather have only a stirring or circulating device in a static liquor tank. This stirring or circulating device (agitator) may be located on the bottom of the liquor tank or, in simple embodiments, on the side. During the washing operation, the agitator may carry out a reversing rotational movement with standstill phases, or else may rotate continuously in the same direction. Such washing machines without a rotating drum will be referred to hereinbelow also as “tub-type washing machines”.
In many areas of the world, particularly those having a shortage of water, it is customary not to discard the washing liquor of a wash cycle immediately after the end of the wash cycle but rather to use the same washing liquor for multiple wash loads one after the other. In this case, the consumer often considers the disappearance of the foam as the washing liquor becomes increasingly soiled to be an indicator of the depletion of the washing power, which nevertheless need not necessarily be the case since although the soil in the washing liquor has a defoaming effect, this need not mean that the cleaning ability of the washing liquor is no longer ensured. For this reason, however, a high foaming capacity is to be regarded as an advantage for consumers. This advantage is even more pronounced, the stronger the foaming capacity remains as the washing liquor becomes increasingly soiled. Such an improvement in the foaming capacity indicates to the consumer a higher washing power and in particular a greater “range” of the washing agent.
Consumers who use tub-type washing machines often counter the loss of foam and the suspected loss of washing power by adding more washing agent. A washing agent which under these conditions produces a stable and esthetic foam will be regarded by the consumer as being of higher performance.
In order to achieve sufficient foam formation and foam stability, it is known to add foam-promoting compounds, so-called “foam boosters”, to washing, cleaning or dishwashing agents. For example, the use of alkyl ether carboxylates as foam-promoting compounds is known from EP 1739161 A1.
EP 0711545 B1 discloses betaines, in particular alkylamidopropyl betaines, as surfactants for cosmetic purposes and as cleaning agents and bases this on the low irritant effect of C8/10APB. DE 2926479 B1 discloses the preparation of C6-C18 alkylamidopropyl betaines.
However, it is known that an excessively high foaming capacity leads to losses in terms of washing performance and, in the washing machines with a rotating drum which are used in Central Europe, to malfunctions caused for example by excessive foaming. The latter effect is admittedly less pronounced in tub-type washing machines, but still occurs to a certain extent. Conventional high-suds washing agents having a formulation rich in anionic surfactant(s) and without any defoaming ingredients generally exhibit a sufficient foaming capacity at the start of a wash cycle. Here, increasing the foaming capacity would lead to excessive foaming, even in these tub-type washing machines. Increasing the foaming capacity in the absence of soil would therefore not be advantageous here.
The same is true in the field of cleaning agents. This is because, in this case too, there is a need for cleaning agents which have a high foaming capacity under high soil loading. In the case of agents for washing dishes by hand, and also in the case of agents for washing clothes by hand, such as travel washing agents for example, it is likewise desired to achieve a good foaming capacity under high soil loading. This is because, in this case too, the foam serves for the consumer as an at least presumed indicator of the cleaning performance. Also in the field of sanitary cleaning products, it would be desirable to provide a product which has an excellent foaming capacity in the presence of high soil loading. This is because, especially in the sanitary sector, the consumer associates a good foam formation with a good and thorough cleaning power against microorganisms.
It was therefore an object of the invention to provide a washing or cleaning agent having improved foaming characteristics under high soil loading. In particular, one object was to provide a washing or cleaning agent which does not give rise to any significant increase in the foaming capacity in the absence of soil, but rather increases the foaming capacity only in the presence of soil. The washing or cleaning agent was further intended to increase the foaming capacity again when added to a washing or cleaning liquor that no longer foams due to high soil loading, and to produce a stable and esthetically pleasing foam even in the presence of relatively large amounts of soil, in particular after multiple successive washing or cleaning cycles.
The inventors have now surprisingly discovered that this object can be achieved by a washing or cleaning agent which contains short-chain alkylamidopropyl betaines in combination with anionic surfactants in particular quantity ratios. The quantity ratio of the short-chain alkylamidopropyl betaines to the total content of alkylamidopropyl betaines must also be set.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with this background of the invention.